A clamp circuit is conventionally provided to protect a switch from induced electromotive force produced by a load (an inductor). In recent years, a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) used as a switch is more and more downscaled and a secondary breakdown voltage is lowered correspondingly. This reduces a value of a current that can flow in the MOSFET in an area in which a voltage between the source and the drain of the MOSFET is high. That is, the safe operation area of the MOSFET is narrowed. In this case, the MOSFET has a high risk of being broken by the induced electromotive force from the load.
Accordingly, it is conceivable to lower the breakdown voltage (a clamp voltage) of the clamp circuit. However, an active clamp voltage lower than a voltage such as a load dump surge voltage that may be applied during an output-off time cannot be set.